Field of the Invention
The present invention relates to an image forming apparatus which adopts such a system as an electrophotographic system or an electrostatic recording system. More specifically, the present invention relates to an image forming apparatus that supplies toner to an apparatus body by rotating a cylindrical toner container that contains the toner.
Description of the Related Art
Conventionally, there are wide variety of applications of an image forming apparatus using an electrophotographic system. The applications include a copier, a printer, a plotter, a facsimile machine, and a multifunctional apparatus having plural functions of these. In these image forming apparatuses, fine powder toner is used as a component of a developer for image formation. As the image forming apparatus that uses toner, an image forming apparatus provided with a container that is filled with toner and is attachable to and detachable from an apparatus body is widely used. The container will be hereinafter referred to as a toner container.
As a toner container, a container disclosed in Japanese Unexamined Patent Application Publication No. 10-333407 that is made of plastics, has an approximately cylindrical shape, and contains toner is widely used. The toner container includes a spiral rib and a discharge port. The spiral rib is formed by a spiral recess defined on the circumferential surface of the toner container so as to project toward the inside of the toner container, and the discharge port is provided in one end portion of the toner container. In the case where this toner container is rotated in a normal rotation direction, as a first rotation direction, by a drive source, the contained toner is conveyed by the rib toward the discharge port and discharged through the discharge port.
This image forming apparatus is also provided with a toner hopper that is capable of reserving the toner supplied from the toner container attached to the apparatus body and of supplying the reserved toner to a developing unit. The toner hopper is provided with a supplying screw that rotates, and the toner is supplied from the toner hopper to the developing unit by the rotation of the supplying screw. The toner hopper is provided with a toner detection sensor, and the toner is supplied from the toner container to the toner hopper when a control unit does not detect the toner in the toner hopper by the toner detection sensor. The amount of toner discharged from the toner container may sometimes vary depending on the amount of toner in the toner container even if the rotation speed is the same. However, the toner hopper can supply a stable amount of toner to the developing unit even in the case where the amount of toner discharged through the discharge port along with the rotation of the toner container is not constant because the toner hopper reserves a predetermined amount of toner.
In addition, in the case where the toner detection sensor does not detect the toner in the toner hopper for several consecutive times, the control unit determines that the image forming apparatus is in a toner-end state in which a desired amount of toner cannot be supplied to the toner hopper due to decrease in the amount of toner remaining in the toner container. In this case, the control unit displays on a display unit a screen to prompt a user to replace the toner container to notify the user that the time to replace the toner container has come.
However, in the image forming apparatus according to Japanese Unexamined Patent Application Publication No. 10-333407 described above, the control unit rotates the toner container only in the normal rotation direction. Thus, clogging with toner may occur in the vicinity of the discharge port of the toner container in the case where the fluidity of the toner has decreased in, for example, a high-temperature and high-humidity environment. If the clogging with toner occurs in the toner container, the discharge performance of the toner from the toner container will decrease. This will cause a supplement malfunction from the toner container to the toner hopper and the control unit will be no longer able to detect the toner in the toner hopper by the toner detection sensor. This may cause a detection error in the detection of the amount of toner in the toner container by the control unit and may cause a false detection of toner shortage, which may cause the screen for the replacement of the toner container to be displayed even when the amount of toner remaining in the toner container is sufficient.